Touch technologies are commonly used as input devices for a variety of products. The usage of touch devices of various kinds is growing sharply due to the emergence of new mobile devices such as Personal Digital Assistants (PDA), tablet PCs and wireless Flat Panel Display (FPD) screen displays. These new devices may not be connected to standard keyboards, mice or like input devices, which are deemed to limit their mobility. Instead there is a tendency to use touch sensitive digitizers of one kind or another. A stylus and/or fingertip may be used as a user touch. One kind of touch sensitive digitizer is a touch screen.
U.S. Patent Application Publication No. 2009-0095540, entitled “Method for Palm Touch Identification in Multi-Touch Digitizing Systems,” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a method for classifying input to a multi-touch sensitive digitizer that is obtained from a body part, as inputs invalid for user interaction and inputs valid for user interaction. The method includes identifying a plurality of discrete regions of input to a digitizer sensor, determining spatial relation between at least two of the regions, and classifying one of the at least two regions as either valid input region or invalid input region based on the spatial relation determined between at least two regions. An invalid region can be input resulting from palm interaction and valid input can be input resulting from a finger tip interaction.
European Patent Publication EP1717684, entitled “Method and apparatus for integrating manual input,” the contents of which is incorporated herein by reference, describes an apparatus and methods for simultaneously tracking multiple finger and palm contacts as hands approach, touch, and slide across a proximity-sensing, compliant, and flexible multi-touch surface. Segmentation processing of each proximity image constructs a group of electrodes corresponding to each distinguishable contact and extracts shape, position and surface proximity features for each group. Groups in successive images which correspond to the same hand contact are linked by a persistent path tracker which also detects individual contact touchdown and liftoff.
U.S. Pat. No. 7,843,439, entitled “Touch Detection for a Digitizer” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a detector for detecting both a stylus and touches by fingers or like body parts on a digitizer sensor. The detector typically includes a digitizer sensor with a grid of sensing conductive lines, a source of oscillating electrical energy at a predetermined frequency, and detection circuitry for detecting a capacitive influence on the sensing conductive line when the oscillating electrical energy is applied, the capacitive influence being interpreted as a touch. The detector is capable of simultaneously detecting multiple finger touches.
U.S. Patent Application Publication No. 2011-0310040, entitled “System and Method for Finger Resolution in Touch Screens,” assigned to N-Trig., the contents of which is incorporated herein by reference, describes a system and method for identifying a plurality of interaction with a digitizer sensor. There is described a method for distinguishing a multiple-finger touch zone from touches by other relatively large objects, such as a palm and a method for discriminating between the multiple finger touches.